Here's a breakdown:

* Force: A push or pull that can change an object's motion or shape.

* Contact Force: A force that arises when two objects are physically touching.

Examples of Contact Forces:

* Normal Force: The force that a surface exerts on an object that is resting on it (think of a book on a table).

* Friction: The force that opposes motion between two surfaces in contact (think of a sled sliding on snow).

* Tension: The force exerted by a rope, string, or cable when pulled taut (think of a weight hanging from a rope).

* Air Resistance: The force that opposes the motion of an object through air (think of a parachute).

Important Note: While we often talk about surfaces, contact forces can also occur between objects that aren't perfectly flat. The key is that they have to be touching.